Quick change systems for tools are known for a quick tool change of rotating tools like mills, drills and similar, wherein the quick change systems operate according to an inductive principle (cf. DE 39 25 641 A1). Thus, tool holders are used for receiving the tools to be clamped, wherein the tool holders have a clamping sleeve whose receiving bore hole is smaller than the exterior diameter of the tool shaft of the tool to be clamped. The induction coil that is concentrically applied to the clamping sleeve and fed by a power generator with AC power or pulsed DC power with a frequency of e.g. 10-50 kHz generates Eddy currents in the clamping sleeve based on the introduced magnetic flux field of the induction coil, wherein the Eddy currents cause a heating of the clamping sleeve and thus a respective expansion of the receiver bore hole of the clamping sleeve. The tool which is then inserted with its shaft into the receiver bore hole of the clamping sleeve is supported through a shrink fit and friction locking within the receiver bore hole of the clamping sleeve after respective cooling of the clamping sleeve. For removing the tool, the clamping sleeve is inductively heated again so that the receiving bore hole is expanded accordingly and the tool can be removed easily. In order to facilitate controlled heating of the clamping sleeve, so called magnetic flux concentrators are known (c.f. “Steel Heat Treatment Handbook”, Marcel Dekker, IR, INC 1997, Chapter 11A, Induction Heat Treatment) which are arranged in particular on both face sides but also at the outer circumference of the induction coil and which bundle magnetic flux lines generated by the induction coil and insert them in a targeted manner into the portion of the clamping sleeve to be heated. Magnetic flux concentrators of this type can be formed from so-called transformer plates which are arranged at the faces of the induction coil in an annular manner or the magnetic flux concentrators are made from a ceramic oxide material, in particular ferrite. These materials are characterized in that they are magnetically conductive but not electrically conductive.
Known inductive clamping and unclamping devices with magnetic flux concentrators disposed at the front face of the induction coil often use annular concentrator elements (c.f. JP 49-10034 or DE 199 15 412 A1). In the known devices, the annular concentrator elements not only extend over the face of the induction coil but they extend at least partially also over the free face of the component to be heated for clamping. However, it is a disadvantage of these devices that they are respectively only configured for receiving components, thus tools, with a particular diameter which is detrimental in particular for tool changing devices since typically tools with different diameters have to be clamped alternatively, wherein different clamping sleeve sizes are then required for the tools with different diameters.
This not only makes the quick change system more expensive, but also makes its application more difficult.
In order to overcome this disadvantage, it is known from DE 10 2005 014 984 A1 to use a multi-component induction coil configuration which includes in particular two coil units which are placed onto a clamping sleeve as a concentric assembly and which are adjustable relative to one another in axial direction with respect to the rotation axis defined by the clamping sleeve. This facilitates adapting the length of the induction coil assembly to the respective size of the clamping sleeve used. It is known in the art that larger clamping sleeves are used for tools with larger shaft diameters, wherein the clamping sleeves have a greater fit length for clamping a tool shaft than clamping sleeves for tools with smaller diameters. Through a respective axial adjustment of the coil units of the induction coil configuration relative to one another adapted to the respective sizes of the clamping sleeves, an inductive clamping device of this type can be used for different clamping sleeves and thus tool diameters. In order to also facilitate a good induction of the magnetic flux lines generated by the induction coil assembly into the clamping sleeve for tools with different diameters, the known device is also provided with an adjustment of the diameter of the magnetic field concentrator in addition to the axial adjustment of the induction coil assembly, wherein the magnetic field concentrator is formed in the known device through concentrator elements through aperture type concentrator elements grouped in a ring shape, wherein the concentrator elements overlap one another and are radially pivotable in inward direction along a radial plane orthogonal to the rotation axis defined by the clamping sleeve. Thus, the aperture shaped concentrator elements can be pivoted in a suitable manner into a respective overlap with the free faces of clamping sleeves with different sizes. The axial adjustment of the induction coil assembly and the radial adjustment of the concentrator elements is coupled with one another and performed through a rotatable adjustment ring through a rotational position of the adjustment ring, wherein the rotational position of the adjustment ring determines the relative axial position of the coil units which are moveable relative to one another and also the radial pivot position of the aperture type concentrator elements. This device has proven useful in practical applications, but can still be improved in particular with respect to automating processes, but also with respect to a desired controlled and optimized introduction of the magnetic flux lines bundled by the concentrator elements into the clamping sleeve to be heated for receiving the tool.